Gravitational wave forms for a three-body system in Lagrange's orbit: parameter determinations and a binary source test

TL;DR

This paper derives gravitational wave forms for a three-body Lagrange orbit system, solves the inverse problem to determine source parameters from wave observations, and discusses distinguishing binary sources from three-body systems.

Contribution

It provides an analytic derivation of gravitational wave forms for a three-body Lagrange system and introduces a method to infer source parameters solely from wave data.

Findings

Derived wave forms at multiple multipole orders.

Solved inverse problem for source parameter determination.

Discussed criteria to distinguish binary from three-body sources.

Abstract

Continuing work initiated in an earlier publication [Torigoe et al. Phys. Rev. Lett. {\bf 102}, 251101 (2009)], gravitational wave forms for a three-body system in Lagrange's orbit are considered especially in an analytic method. First, we derive an expression of the three-body wave forms at the mass quadrupole, octupole and current quadrupole orders. By using the expressions, we solve a gravitational-wave {\it inverse} problem of determining the source parameters to this particular configuration (three masses, a distance of the source to an observer, and the orbital inclination angle to the line of sight) through observations of the gravitational wave forms alone. For this purpose, the chirp mass to a three-body system in the particular configuration is expressed in terms of only the mass ratios by deleting initial angle positions. We discuss also whether and how a binary source can be distinguished from a three-body system in Lagrange's orbit or others.